The figure represents an increase of more than half a million viewers in recent weeks and is almost double the audience the show pulled in on its debut a year ago.
Thursday's edition drew an average of 3.18 million, a 21.3% audience share, in the 5pm hour but was still narrowly pipped by BBC Two's Weakest Link, which had 3.21 million (20.4%). Neighbours was still the slot leader with 3.24 million (19.5%) for BBC One from 5.35pm, while on Channel 4, Richard and Judy had just 1.56 million (10.4%).
EastEnders was the day's top performer with 11.83 million (52.3%), keeping Emmerdale in second on 8.84 million (43%).
ITV1 took the lead at 8pm, with The Bill averaging 6.81 million (28.8%) and fourth place for the day. BBC One's Bleak House held a steady 5.59 million (23.9%) before ratings dropped off to 4.46 million (18.7%) for The Queen's Cavalry. Gordon Ramsay's F Word delivered 2.44 million (10.4%) for Channel 4, just ahead of BBC Two's Restored to Glory with 2.2 million (9.3%). Five's How Not to Decorate mustered 1.24 million (5.2%) for fifth place in the hour.
ITV improved its lead at 9pm, averaging 8.3 million (35.4%) for Martin Clunes drama Doc Martin despite tough competition (5.78 million, 24.7%) from BBC One's Spooks. Channel 4 was third with 1.87 million (8%) for the conclusion of Wanted: New Mum and Dad, leaving BBC Two (0.74 million, 3.1%) and Five (0.58 million, 2.5%) with embarrassing figures for The Last Stand and Dream Business.
BBC One edged back at 10pm with 5.03 million (25.4%) for its news bulletin while on ITV1, the Joan Collins-fronted celebration The Avengers - Must See TV settled for 3.03 million (15.3%). New comedy Sensitive Skin put in a promising 1.99 million (10.1%) for BBC Two and on C4, Travolta movie Domestic Disturbance averaged 1.94 million (13%) through 11.40pm. The pilot episode of House, MD drew 1.3 million (7.4%) to Five.
Repeats were flavour of the day in multichannel homes, with Only Fools and Horses managing a notable 371,000 (2.2%) for UKTV Gold from 9pm.
ITV2 movie Red Heat had 340,000 (2.4%) between 9pm and 11.05pm, while on sister channel ITV3, spinoff doc Doc Martin - Behind the Scenes enticed 311,000 (2.5%) in the 10pm hour.
Other notable performers included Sky One's Secret Life of Suburbia (285,000, 1.7%), Living TV's CSI (272,000, 3.8%) and Hallmark's Law & Order: Special Victims Unit (236,000, 1.9%).